This book investigates the ESP claim that tertiary level ESL students should be given reading proficiency tests in their own academic subject areas, and studies the effect of background knowledge on reading comprehension. It is set against a background of recent research into reading in a first and second language, and emphasises the impact that schema theory has had on this. Results from versions of the International English Language Testing System (IELTS) reading subtests are analysed quantitatively and qualitatively. Rhetorical function, academic/topic specificity, EAP teacher uncertainty, student familiarity and varying background knowledge are all identified as causes of variation in the appropriacy of reading passages. The book concludes by considering the implications of the findings for future test construction and research into reading.